Sorry to be blunt, but you are just combining terms and ideas without understanding. This is a classic pseudoscience. You can be sure your problems are not in any way related to argon coming from the water supply, you are just making it up.
Since Argon is heavier than N2 and O2 is it concentrated at the floor?
No, it is not. Thermal mixing is way too strong for that.
Is there a good graph over density of the Ar, N2 and O2 at different temperatures?
No need for graphs, these can be easily estimated from ideal gas equation and molar masses. It won't help you, as to separate gases with different molar masses one needs very high columns and very low temperatures, there is no measurable separation in a typical room conditions.
apparently Argon can act like CO and take the spot where O2 goes on the red blodcells leading to problems.
No, it can't.
Argon comes for a Potassium isotope and I have a lot of Potassium in the ground.
Yes, K-40 decays into Ar. No, amounts of Ar produced this way are many orders of magnitude lower than the amount of argon present in the air, so potassium is not a real local source of Ar.
If you have headaches I suggest you consult your GP, this will be definitely more effective than looking for answers in places you don't understand.